Photolithography process is a very important process of the semiconductor manufacturing technology, which transfers patterns on a mask to a substrate by an exposure process. The photolithography process is a core step of the manufacturing of large scale integrations (LSIs). The complex and time-consuming photolithography process of the semiconductor manufacturing technology is mainly performed by corresponding exposure apparatus. Further, the development of the photolithography technology or the improvement of the exposure apparatus are mainly focused on three specifications including feature size, overlay resolution, and yield.
In the manufacturing of a semiconductor device, the photolithography process may include three main steps: changing wafers on the wafer stages; aligning the wafers on the wafer stages; and transferring patterns on the mask to the wafers. These three steps may be sequentially repeated on the same wafer stage.
Since the photolithography process is a key step of the semiconductor manufacturing process, how to improve the yield of an exposure apparatus in the practical manufacturing process has become a very important topic. Various exposure apparatuses with twin-stages have been developed in past a few years in order to further increase the yield of the exposure apparatuses.
FIG. 1 illustrates an existing exposure apparatus with twin-stages. The exposure apparatus includes a first stage 101 and a second stage 102 for holding wafers; an alignment detection unit 103 for detecting align marks on wafers and aligning wafers; a mask stage 107 for holding a mask 108; an optical projection unit 104 under the mask stage 107 for projecting light through the mask 108 on the wafers on the first stage 101 or the second stage 102 and performing an exposure on the wafers; and an illuminator 109 above the mask stage 107 for providing an exposure light.
An exposure process using the existing tool may include sequentially: aligning the first wafer 106; moving the first stage 101 under the optical projection unit 104; and performing an exposure on the first wafer 106 using the optical projection unit 106 which projects light through the mask 108 on the first wafer 106. At the same time, a second wafer 105 may be installed on the second stage 102, and moved under the alignment detection unit 103. The alignment detection unit 103 may detect the alignment mark on the second wafer 105 on the second stage; and the second wafer 105 may be aligned. After the first wafer 106 is exposed, a new wafer may be installed on the first stage 101, and the first stage 101 with the new wafer may be moved under the alignment detection unit 103. The alignment detection unit 103 may align the new wafer. At the same time, the second stage 102 may be moved under the optical projection unit 104, and the second wafer 105 may be exposed by the optical projection unit 104.
However, even with such improvements, the exposure efficiency and the yield of the existing exposure apparatuses may still be relatively low. The disclosed methods and systems are directed to solve one or more problems set forth above and other problems.